I have been using SQL for a decade but I never had to connect Oracle database till last week! So, even basics are like learning for me!
• Oracle SQL Developer is the tool similar to SSMS you can download from http://www.oracle.com/technetwork/developer-tools/sql-developer/downloads/index.html.
• You have register the Oracle Server using Server information and credentials
• You can just execute Oracle queries similar to SSMS
o SELECT * FROM user_tables;
o SELECT * FROM v$version;
Quick reference link for first time oracle users: http://viralpatel.net/blogs/useful-oracle-queries/
NOTE: Provide correct SID/Service Name while connecting to Oracle Server. Get correct values from Oracle DBA!